Automatic electric regulator or overload limiting apparatus



30, 1930. A. BARB GELATA 1,787,303

AUTOMATIC ELECTRIC REGULATOR OR OVERLOAD LIMITING APPARATUS Filed June 28, 192

M/vw-A. 59

a b v. 62

Inventor 1 Angelo Barbagelaba y M F His Attorneg.

Patented D. 30,l1930 nun-E .jsTA s ATE-NT OFFICE I I ANGELO BARBAGELATAQ-OFMILAN, IT LY, AssiGNoR "r0 GENERAL ELECTRIC conjran'r, acortrona'rron or nnwronx .Amomm m nors-11o uncommon 0R- o EB OAD LIMITING APPARATUS .a ii'eatiiimedium 28,1328, Serial not iaoaa ana in Italy- July-9, 1925.

My invention relates toaautomatic electric] regulators or overloadf limiting apparatus provided with aj slngle .current-.respons1ve operating element or winding, and more par ticularly to means ior. controlling the enerA gization of the operating.elementorwinding 7 when said-regulators or overload apparatus are usedto control tllBCOIlClllJlOl] of energi- 'zation of an electric circuit.

'l/Vhen using automatic electric current regulators, .relaysor similar load limiting devices, having a singleonefphase currente.

responsive operating element vin connection with a polyphase circuit, as for: example a three-phase circuit,.it.is .well known that two current transformersmay be associated with two of the phase conductors ofthe three I phase circuit with the secondaries crosscon p vide a new and improved arrangement-of apparatus whereby a single one-phase current nect-ed in accordance with the reversed V principle in such a manner as to excite the operating element in accordance with the vectorial resultant ofthe current in each of thephasesin which the current transformers areconnected. Such anarrangement effects proper energization of the single-element de-' vice under. balanced currentcondltlons but.

under conditions of unbalance'due to unbalanced loads, single-phase short CIICLUtS, or

faults from aphase conductor to ground-the energizationoi the single element devicezmay be too great orinsufficient to obtain the same. condition of regulation or protection. roban outside phase'conductor of the'loadciiw cult, may cause the ClBVICG tO regulate or limlt the current in one phase conductor to a value higherthan the predetermined value for balanced current conditions with-thesame calibration of \the controlling device. .On the other hand, if the current transformers are connected in the outside conductors leading I from thegenerator,and-the generator sup' plies current to a load devicethrough step-upf transformers connected in delta-star or stardelta ashort circuit between the middle and ,an'outside wire of the load device would re sultin zeroenergization of the single element devicei'supplied through the-eross+con11ected current transformers and thereby provide no regulation or protection.

An object of my inventionisto-pmvide a new andimprcved arrangement of apparatus .whereby a single 'operatingielement or winding of a iregulator, overload protective device, or other similar currentcontrolling device maybe energized fromapolyphase electric circuitin accordance with the current lnaphase conductor in which the current bears a predeterminedorder-of magnitude with respect to the current in-another phase conductor.

. Another object of my-invention isto proresponsive operating element of a regulator, overload protective device, orother similar current controlling device may be energized in accordance with the current in a phase conductorwhich has thelargest current flowing therein.

In orderto'securethe desired energization of the single current responsiveelement or,

windings of the regulator- 01' protective d e-.

vice froma polyphase circuit under various operating conditions of unbalance, I provide currenttransformersin different phase 0011- ductors and means for changing the-connectionsof the single current.responsiveelement to a single transformer-in a-phase cenductor in which, for example, the largest current is flowing.

My invention will he better understood from the following eescriptiontaken-in connection wtli the accompanying drawing and its scope will be ed claims.

gInthc accompanying drawing Fig l is a diagrammatic representation of one embodimentof mydnvention adapted foruse inconnection withathree-phase circuit and Fig.2. is aniodification of the arrangement shown in Fig. 1.

InfFig. 1 of the ,drawingI have shown a three-phase distribution circuit comprising pointed out Lin-the append;

conductors a, Z) and 0. Current transformers 4, 5 and 6 are connected in the phase conductors a, Z) and a, respectively, and are provided with secondary windings 7, 8 and 9, respectively. Three differential main relays 1, 2 and 3 and two auxiliary relays 10 and 11 are shown in their usual position of rest (off-position) and are provided to select the transformer secondary winding which is to provide energization for the current regulating or protective device.

The differential relay 1 may take the form of well-known relays of this type suitable for use on alternating current circuits and comprises two operating coils 12 and 13 for actuating a plunger 14 which carries upper and lower movable contacts for bridging stationary contacts 17 and 18, respectively. Each operating coil tends to move the plunger associated therewith in the direction indicated by the arrows so that if coil 12 has the greater energization the plunger will rise but if coil 13 has tl e greater energization the plunger will be maintained in its lower position. Similar to differential relay 1, differential relay 2 comprises operating coils 19 and 20 and a plunger 21 which carries upper and lower movable contacts 22 and 23 for bridging stationary contacts 24 and 25, respectively, and differential relay 3 comprises operating coils 26 and 27, a plunger 28 which carries upper and lower movable contacts 29 and 30 for bridging stationary contacts 31 and 32, respectively. The operating coils 12 and 19 of relays 1 and 2, respectively, are energized in accordance with the current in phase conductor a from the secondary winding 7 of current transformer 4, while the coils 13 and 20 operating differentially with coils 12 and 19, respectively, are energized in accordance with the current in phase conductors b and 0, respectively, from the secondary windings 8 and 9 of current transformers 5 and 6. The operating coil 26 of relay 3 is energized in accordan'ce with the current in phase conductor Z) from the secondary winding 8 of current transformer 5 and the operating coil 27 is energized in accordance with the current in phase conductor 0 through the secondary winding 9 of current transformer 6. In other words, relay 1 is actuated in accordance with the relative magnitudes of the currents in phase conductors c and b; relay 2 is actuated in accordance with the relative magnitudes of the currents in phase conductors a and c; and relay 3 is actuated in accordance with the relative magnitudes of the currents in phase conductors b and 0.

The auxiliary relay 10 comprises an operating coil 33 for actuating a plunger 34. The plunger actuates three movable contacts 35, 36 and 37 which serve to bridge stationary contacts 38, 39 and 40 in the lower position of plunge)" and to bridge stationary contacts 41, 42 and 43 in the upper position of plunger 34. Similarly, auxiliary relay 11 comprises an operating coil 44 and a plungor 45 which carries three movable contacts 45, 46 and 47 for bridging contacts 48, 49 and 50, respectively, in the lower position of plunger 45, and contacts 51, 52 and 53, respectively, in the upper position of plunger 45. The energizing current for the operating coils of the auxiliary relays is obtained from a station service bus or any other convenient source and is indicated by the plus and minus signs. The auxiliary relays are provided to change over the connections from the operating element R to the desired transformer secondary winding and to maintain the transformer secondaries not connected to R in a closed circuit.

Although my invention is applicable for use in connection with various types and arrangements of current regulators and automatic electric regulating, or overload limiting apparatus provided with a single current responsive operating element or wind ing, 1 have shown very diagrammatically the operating element R, by way of example, as controlling the excitation of the supply for the distribution circuit in order to control its condition of energization. As shown an. alternating current generator G is connected to energize the distribution circuit comprising conductors a, b and 0 through suitable switching means S. The generator is provided with a main field win g F which in turn is connected to be energi zed by an ex citer E. The exciter is provided with a field winding which is connected in shunt to the armature of the exciter through a regulating resistor H. The regulating resistor is shunted by a circuit comprising contacts K which are arranged to be closed when the winding R is energized by a current below a predetermined value and arranged to be opened when energized by a current above a predetermined value. It will be observed that when the contacts are opened the resistor H is inserted in series with the exciter field so that the generator field excitation reduced to limit thereby the current supplied by the generator under balanced overload conditions or under unbalanced conditions of overload or short-circuit.

The single one-phase current responsive device R is connected to the secondary winding 9 of the current transformer 6 in conductor c. The connections in the diagram do not change for any condition of practically balanced load or overload on the three phases. In case of unbalanced overload or of single phase short-circuit, if the overload phase conductor be c, the connections do not change and the regulator will keep the current in the circuit a, F) and 0 within given limits. It may be interesting to note that when L is the largest current, even if I, be

regulator R on phase a.

ivy-smo lar enthanl b suchan amount as to' en in l ergiz'e relay 1E and the latter closes the upper.

stationary contacts 17, no change 'is-ciiected in the connection ofR to-the-se condary'winding ofcurrent transformer 6.7 c

If in a single-phase overload the largest currentbe in phase a,then Lbeing grea ter than 1 and I relays l and 2 are energized and close the. circuit of the first auxiliaryre lay which acts to effect the insertion of the switching and connections for changing the energization of the regulator or protective deviceR from the current transformer secondary w nding 9 to the-secondary winding 7 of current transformer 4 in conductor a is as follows: Since the magnitude of the current in phase conductor a is assumed to be greaterthan the current in phase conductor 7) -o1"c,rrelays l and 2 are moved to a posi-'- tion to cause upper contacts and 2:2 to

bridge stationary contacts 17 and 24 and open stationary contacts 18. Uponclosureot contacts l'7and 24 a circuit 15 completed for up:

crating coil 33 ot aimiliary relay ll) which in turn moves its plunger 34 to its'upper position to close-contactsll', 42 and 4:2 When contacts 41 close a circuit is con'ipleted from the upper terminal of the secondary windclosed circuit for the secondary windings 8, andQ of the transformers in conductors Z2 and c. I a

Similarly whenthe largest overload afiects phase 5, the main relay only would be energized (whiist relay *1 is'lzept down by the fact that L, 1,) and consequently the anailiary relay 11 would enter into action, con-.

necting the re ulator on the phase conductor 7) in a manner which will be obvious from the operation hereinbefore' described.

So with the above described arrangement, the regulator is always automatically connected to. a single transformer viz. to the one ofthe phases affected by the highest load, thus'permitting-the regulator or protective device 13- to be energized hythe highest sate load, whatever may happen in-the system as to overload or short-circuits.

Fig.l is entirely diagrammatic and the various relays shown can be ofany known design. The differential main relays l, 2 and 3 have'a position of rest secured by the weight of the armatures butsprings or s1m1-' lar. biasingmeans will occur toithose skilled inthe and may fibeused f preferred. Smcethere *mUSt'ZbB 'acertain dilierence in T he sequence off the currentscirculating in the two coils ofeach relay to lift the arniature tmthe upper position, the connectionof the regulator will a be changed-from one p'haseto al'iothei only if,

the diflerence in the current values between each phase and the overload phase reaches a certain finite-amount. It is easy to realize however that,

wing to the limits within which this difi'erencecan be kept, theabove limiting condition is unimportant for the scope of the present invention, asitheapparatus concerned are neverto beconsidered precisiondevices. 1 a v i j p i From the general nconnection diagram shown in Fig. 'ltliemodification ofmy invention shown in Fig. 2 may be immediately detwo currived. In this arrangement onl p with the rent transformers are associate three-phase circuitcomprising conductors similarly designated as in Fig.1 by a, band c. Current transformers 54 and #55 having sec ondary windings 56 and 57, respectively, are connected in phase conductors b and-0, respectively. [A differential type of relay similar to the relays 1, 2 and 3 ofFig. 1 is arranged to connect the device R across the transformer secondary winding'oti or=57, and comprises operating coils 58 and 59 and a plunger 60 carrying movable contacts 61 and 62. When the lun 'er 6O is'in its'lower' osition as shown) movable contacts (ll and 62 are arranged'to bridge stationary contacts63 and 64,'respectively, and when plunger-60-moves to its upper positioncontacts 61 and'62 are arranged to bridge stationary contacts 65 and 66, respectively. For the condition shown device His connected acrossthe transformer secondary winding 57 of trans'for'merfi55 associated with conductor 0 and the secondary winding 56 of transformer 5d associated-with conductor Z) is closed through coil 5843f the relay and contact 61. If the currentin phase its) conductor 6 becomes greaterthan the current in phaseconductor 0 contacts 61 and 62 are moved to bridge stationary contacts 65 and 66. This connects the device R acrossthe secondary winding 56 of transformer 54 and closes the circuit of the secondary winding 5 57 through the relay operating coil 59. The arrangement just described shows how the auxiliary relays can be eliminated when'it is suflicient to excite the device R from either of two current transformers but the auxiliary relays are retained whenever other practical working conditions may'require it.

According to the arrangement shown in F ig, 2 the regulator or protective device R is 1 usually connected to one of the two current transformers, but as soon" as thecurrent in the other transformer becomes greater by a certain amount, the differential relay switches-on automatically .the latter trans+ former. V r i V So, withthe arrangement shown in the modification ofFig. 2, the regulator is alformer, the current may be held to avalue double of that of the other two.

WVhile I have shown and described several particular embodiments of my invention and disclosed the features of it and its possibilities with a few practical illustrations, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention and I, therefore, aim in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a polyphase electric circuit, means comprising an operating element for controlling the condition of energization of said circuit, and switching means operative upon the occurrence of. unbalanced conditions in said circuit for selectively effecting energization of said operating element in accordance with the current in a phase conductor in which the current therein bears a predetermined order of magnitude with respectto the current in another phase conductor.

2. In combination, a polyphase electric circuit, means for controlling the condition of energization of said circuit comprising a winding, and switching means operative upon the occurrence of unbalanced conditions in said. circuit for connecting said winding to be energized from a phase conductor in which the current is of greater magnitude than the lowest current in a phase conductor of the unbalanced circuit.

3. In combination, a polyphase electric circuit, a device for controlling the condition of energization of said circuit comprising a single one-phase operating element, and switching means operative upon the occurrence of unbalanced current conditions in said circuit for connecting said operating element to be energized. from a phase conductor in which the largest current is flowing.

4:. In a system of distribution, a p-olyphase electric circuit, means for controlling the current in said circuit comprising a winding, a plurality of current transformers associated with phase conductors of said circuit, and switching means connected to be responsive to the relative magnitudes of currents in a plurality of phase conductors and operative upon the occu rence of unbalanced current conditions in said circuit for selecting and connecting a single current transformer to energize said winding.

5. In a system of distribution, a three gle current-responsive winding, a current transformer connected in each phase conductor of said circuit, switching means for controlling the connections from the terminals of said current responsive winding to one of the secondary windings of said current transformers, and a plurality of relays each responsive to the current from a pluvrality of said current transformers and operative upon the occurrence of unbalanced current conditions in said circuit for controlling said switching means to effect a connection from said current responsive wind: ing to the secondary winding of a current transformer in which the largest current is circulating.

6. In a system of distribution, a threephase electric circuit, means for controlling the current in said circuit comprising a single current-responsive winding, a current transformer connected in each phase con-- ductor'of said circuit, switching means for connecting said current responsive winding to the secondary winding of one of said current transformers and for closing the secondary circuits of the remaining transformers, and a plurality of differential relays each-responsive to the current circulating in two of "he phase conductors of said circuit for controlling said switching means.

7. Ir a polyphase system, in combination, a regulator for governing supply to the sys tem, detecting devices operable independently from respective phases of the system, and connections between said devices and said regulator providing for energization of the latter upon operation of any of said devices.

8. In a polyphase system, in combination, a control device, means for energizing the same from the several phases, and detecting devices operable independently from the respective phases to cut in the control device.

9. In a polyphase system, the combination with the phase lines, of a current-limiting regulator for regulating current supply to the lines, transformers for energizing the regulator, the respective transformers being energized from respective phase lines, and detecting devices operable from the respective phase lines for connecting the transformers to the regulator.

10. In a polyphasesystem, the combination with a current regulator for regulating current supply to the system, of transformers energized from the respective phases, and detecting devices energized from the respective phases for connecting the respective transformers to the current regulator.

11. In a system of distribution, a polyphase electric circuit, means comprising a winding for controlling said circuit, a plurality of transformers connected one to each phase of said polyphase circuit, and switch ing means for selectively controlling the energization of said winding from one of said transformers. i i

12. In a system of distribution, a polyphase electric circuit, means for controlling the current in said circuit comprising a single current-responsive winding, a plurality of current transformers connected one in each phase conductor of said polyphase circuit, and switching means for selectively connecting said Winding to be energized from one of said current transformers.

Signed at Milan, Italy, this 10th day of June A. D. 1926.

ANGELO BARBAGELATA. 

